Children are different
from each other both when they are young and after they mature. Why is that?
There was a time when no one hesitated with the answer; they're different
because they were reared differently. Some were spanked, some were not. Some
received authoritarian parenting, some permissive, some authoritative. Some were
toilet trained early and harshly, some were left to cry in the crib and some
were cuddled, and so it went. Anyone reading this review knows this story and
knows that the emphasis was on parenting and genes were not a part of the
account.

Behavioral
genetics, by studying identical twins, fraternal twins, other siblings and
adopted children altered that account in the late twentieth century. It showed
convincingly that genetic variance accounts for a good deal of trait variance,
leading to the (oversimplified) formulation: trait (phenotypic) variance =
genotypic variance + environmental variance. While this seems vaguely like
common sense, the admission of genotype as an important factor in human
development placed almost the entire corpus of developmental research under
suspicion for not controlling for genes. Agreed, children whose parents read to
them regularly become better readers. But with genes in play the correlation
no longer implies that reading to children causes them to become better
readers. Thousand of dissertations, scholarly articles and parenting paperbacks
need to be cast into the flames of discarded paradigms. But behavioral
genetics went further. It failed to detect any significant parenting effects
from within the environmental realm of the causation of traits (The exception
is pathologically abusive parenting.)

Questions
lingered. If environmental variance accounts for roughly half of phenotypic personality
variance, why are siblings raised at home so different? They seem to share
half the genotype and the entire environment. Even more curiously, why are
identical twins reared together so different when they share all of their genes
and all of the environment? Why were the Iranian conjoined twins Laleh and Ladan
so different when their genes and environments seemed all but identical? No
Two Alike, this wonderful new book by Judith Rich Harris, takes on this
most difficult of questions. While behavioral genetics has established that
genes have an important role in the development of human differences, it is
Judith Harris who seeks to uncover the complicated and subtle mechanisms
through which the environment in its broadest senses leaves its marks.

In
developmental psychology when Robert Plomin of Kings College, London speaks,
people listen. In 2001 Plomin, et. al. provided a comprehensive
review of the literature in an article, "Why
are children in the same family so different", Canadian Journal of
Psychiatry, 46, 225-233. Where "non-shared" environment denotes
factors that make people different, they wrote, "We also need to
consider the gloomy prospect that chance contributes to non-shared environment
in terms of random noise, ..." They
had failed to detect any systematic factors that separate out children, leaving
the possibility that they become different as a result of chance events. These
singular events are not literally by chance, of course, but they and their
effects are unpredictable. One sibling finds himself in the sights of a bully
and is frequently frightened, another loses control of his bowels in gym class
and gains the long-lasting nickname "shitty", a third has counseling
from a charismatic therapist and devotes herself to psychology. These singular
events alone do not alter lives. They create what Plomin, et. al. refer
to as a, "... subtle interplay of a concatenation of events." They
set something in motion that gains momentum. As Kierkegaard has a character say
in Either/Or, "The smallest of causes can bring about the greatest
of effects." The prospect of admitting these events into the picture is "gloomy"
and the events are "noise" because just as noise grates upon the ear,
singular events grate on a scientist's penchant for regularity.

Judith Harris shook the field of
socialization research in 1998 with her impressive and hugely popular The
Nurture Assumption where she argued (1) that genes are a big part of human
developmental variation, (2) the effects of diverse parenting practices are
restricted to the home, and (3) environmental effects come largely from peer
socialization. In No Two Alike she seeks to fill in the account of how
the variation in the environment contributes to differences among people.

Harris is an unusual figure in academic
psychology. She has no Ph.D. and no academic appointment. She's a reformed
textbook writer from New
Jersey who has become a
leading developmental theoretician. Harris delights in retelling the story of
her ignominious exile from graduate study at Harvard at the hands of Chairman
George A. Miller and her redemption in 1998 when the she received from the
American Psychological Association the George A. Miller Award for her 1995
paper, "Where is the Child's Environment", Psychological Review,
102, 458-489. And Harris, a devotee of mystery writing, is a great
storyteller, relating exchanges with researchers who have tried to obscure the
details of their work under the glare of Harris' keen eye. I can think of no
rival to Judith Harris' ability to spot confounds in research and to suggest
alternative conclusions that are more consistent with the data than the
researcher's own. Let me illustrate:

Harris is not a
researcher, at least in the sense that she does not run subjects, have a
laboratory or seek research funds. As a result she must rely upon the data of
others to support her critiques and the ideas she promotes. This places a
heavy burden to be certain that first, the research she sights is
methodologically adequate to the conclusions drawn and second, that what is
reported, even widely reported, was actually what was done. On this matter,
had Harris been canine she would have been a bloodhound-bulldog cross. Two
examples:

First, Harris long ago concluded
that, within the realm of the non-pathologically abusive, parenting styles have
little effect outside the home. This was argued in The Nurture Assumption
and is argued again in No Two Alike, and God help the researcher who
reports data to the contrary. Following The Nurture Assumption Harris
was invited to a conference on parenting sponsored by the National Institute of
Child Health and Human Development (NICHD). One of the organizers reported to
Harris, "I had to fight to get you on the program" (53). Harris'
only ally present was David Rowe whose The Limits of Family Influence
(1994) preceded Harris' 1998 work. The conference papers were published as an
important anthology, J. G. Borkowski, et. al., Parenting and the
child's world: influences on academic, intellectual and social-emotional
development. (2002). Harris provides an amusing account of the conference
and a very clear description of the issues involved. Socialization theorists,
who for decades had ignored genetic contributions to personality traits in
favor of parenting effects, have now admitted the former into their
conversations. But they continue to reject the behavioral genetic evidence
against parenting effects beyond the home. Their new claim is that parenting
effects are mediated through the genes, through gene-environment interactions, so
that in the same family one child may flourish under harsh discipline while
another withers. They contend as well that these parenting effects are
cancelled out in the behavioral genetic analysis, explaining why no parenting
effects turn up despite their existence. Of course if this were true, then
using parenting research to formulate child-rearing advice would be impossible
since the same recommendations could have opposite effects upon two children.
But Harris denies that it is true in the sense proposed. She agrees that the
effects of parenting will be mediated through the genes of the child, but that
differences as great as to cancel each other out, so-called "crossover
effects", are very rare anywhere in nature. She argues that genetic
mediation tends to have "sensitivity effects" where the consequences
of an environmental variable run in the same direction though to greater or
lesser extents.

One paper at the conference caught Harris'
attention as a serious challenge to her claim that parenting styles do not have
consequences beyond the home. Stephen Suomi does research on Rhesus monkeys at
NICHD. He reported his study that employed two genetic strains of monkeys, one
bred to be nervous or "high-reactive" the other to be calm or "low-reactive.'
The monkeys of both groups were reared by adoptive monkey mothers who were
either good or bad mothers. The "low-reactives" turned out okay
regardless of having good or bad mothers but the "high-reactives"
with bad mothers were social failures while the ones with good mothers were
okay. And the effects of the different mothering persisted even after they
left their mothers. Even with qualifiers about human-monkey differences, this
tended to disconfirm Harris' viewpoint and she needed to be convinced, "What
surprised me was not that monkeys with good foster mothers did well while they
were with their mothers, but that the effects of good mothering persisted ...(61)."
And Harris found Suomi's research sited again in an article by prominent developmentalists
six months later. Since Suomi had been sketchy about his research in the
conference talk, Harris found the location of its full description from the
references in the developmentalists' article. It was in a chapter that Suomi
contributed to an anthology, but upon checking Harris found no reference to the
cross-fostered monkeys. A call to the first author of the developmentalists'
article led to another of the authors who reported that her source was a phone
call from Suomi. Suomi reported by email to Harris that the study involves
thirty-six cross fostered monkeys, eighteen of each strain but nothing of the
results. He promised a monograph in 2000. A literature search turned up a
study with fewer than eight monkeys, meaning that a maximum of four were "high-reactives"
and a maximum of two of those would be raised by bad foster mothers. A later
book chapter reported a "recent" study, but gave no data and no N.
When it came time for Suomi's conference presentation to appear in print in
2002 there was no mention of cross-fostered monkeys.

The second example of Harris'
doggedness (no pun here) involves the revered Harvard developmentalist, Jerome Kagan.
As it happens, Kagan and Harris have several good reasons to think of each
other as kindred spirits. His research from the 1960s pinpointed shyness as a
genetic trait. His study of Guatemalan children emphasized the flexibility of
child development at a time when parents were being warned, in this case by
John Bowlby, that leaving a child with Grammy even for a fortnight could have
serious later implications. And he has been a persistent critic of early
experience theories. But alas, Kagan and Harris drifted into an adversarial
relationship following The Nurture Assumption, afterKagan accused
Harris of ignoringresearch that disagreed with her positions. A point
in question was a claim of Kagan's to have measured children at four months and
at school age. He reports finding that fearful children whose parents
(over)protected them were still timid while those whose parents pushed them to
try new things were not. These are parenting effects beyond the home and on a
trait with a strong genetic base. Newsweek duly reported these results
in its article on Harris. She wanted to know the truth. It turns out that
what Kagan had published, in a chapter of a book in 1994, was a preliminary
report of a study done by one of his Harvard doctoral students. Harris found that
the retests were done, not at "school age" as Newsweek had reported
but at 21 months. Three years later the graduate student published results
that reported retests at four and a half years but eliminated any reference to
child-rearing style for that group.

Finally, Harris notes somewhat
scornfully that Suomi's cross-fostered monkeys and Kagan's once-timid babies
continue to get press, rather like academic urban legends, and the
above-mentioned lead developmentalist is still teaching his students about Suomi's
findings. She tells a third story about the persistent efforts of a lawyer,
Frederic Townsend, to track down the data on which Frank Sullaway drew his
amazing conclusions about birth order effects in his Born to Rebel
(1996). It is a story of insult, threats of lawsuit, obfuscation within the
scientific community and missing data.

Harris is persistent not only
concerning whether research has been done as reported but whether the
methodological assumptions of the research hold water. She criticizes Kagan-type
research for assuming that any changes that take place between time-one and the
retest at time-two cannot be caused by genes. This assumption seems reasonable
since one's genotype does not change over time. But Harris points out that
many genes switch on, and thus turn their effects on, at different times in the
developmental process. One does not conclude that male pattern baldness is not
genetic simply because hair loss begins post adolescence. Her second objection
is that such research neglects the well-documented phenomenon of
child-to-parent effects, that parents alter their behaviors as a result of the
child's behaviors. The child who loves to be read to gets read to and the
child who is a hellion as early as his descent through the birth canal receives
harsh discipline. That these children turn out to be great readers and car
thieves cannot be automatically attributed to parenting styles.

I'll give two more examples of
Harris' expertise at methodological critique. Intervention studies are the
closest that developmental psychologists can get to controlled experiments and
the best way to skirt the correlation-causation problem. This research randomly
selects an experimental and a control group from a population, gives the
experimental group parenting training, and then measures the behavior of the
children of both groups. Harris' interest is in the extra-home child behaviors
since she denies that parenting styles affect it. Philip and Carolyn Cowan from
UC Berkeley do this research as well as anyone and were good enough to supply
Harris with their most recent study. They concluded that if you improve
parent-to-parent and parent-to-child interactions with a four-month program the
child's school performance improves. But Harris was unable find any comparison
between the school performance of the children of the experimental and control
groups. When asked, Cowan responded that they were reporting only on the
children of the parents who improved as a result of the intervention, the
others dropped into the control groups. Harris says, "Hmm. So the
parents who improved as a result of the intervention had kids who did better in
Kindergarten (132)." Just another correlation study. Cowan directed
Harris to studies by Marion Forgatch who works with David DeGarmo. In an
article in a peer reviewed journal (Harris, despite being outside the academy,
has great respect for the peer review process.) Forgatch and DeGarmo created
experimental and control groups, administered an intervention to the
experimental group that sought to reduce "coercive parenting" among
single mothers of young sons and did follow-up reminder calls to the mothers.
They reported that mothers became less coercive and that, "improved
parenting correlated significantly with improvements in teacher-reported school
adjustment (133)." The statistic that was missing from the Cowans' study,
comparisons between control and experimental groups, was provided in this one.
There were no significant differences in school behaviors between the two
groups.

I have taken some time with issues
of both academic sociology and research methodology to show how complex it is
either to establish parent-to-child effects outside the home or to undermine
ideas about them that have been so long and so widely disseminated. And I
wanted as well to give a glimpse at who this person Judith Harris is who has so
shaken the establishment in developmental psychology.

Of course it is easier to critique
than to build. But Harris is not only a critic. In the hubbub surrounding The
Nurture Assumption it was largely lost that the book contained a revised
socialization theory, one that focused upon the effects of peer culture in the
way that previous researchers has emphasized the family. No Two Alike contains
a theory about how it is that this system works. How, over and above our
genotype, does environment shape who we are? Harris takes as her challenge
the most difficult case. How does environment cause identical twins to have
such different personalities? Her theory is ingenious, subtle and original.

Harris seems to believe that her
theory is wedded to evolutionary psychology and to the theory of the "modular
mind". I don't think that it is. It can be clearly and completely stated
independently of both of these and that it is stronger for its independence.
If evolutionary psychology were simply be the idea that we will have a better
understanding of mind and behavior as evolutionary scientists learn more, it
would be both true and innocuous. But its proponents, like Judith Harris'
friend Harvard's Stephen Pinker, think of it as more, as an actual methodology,
one that includes "reverse engineering". This in general means asking
about some existing but unexamined entity what it must be like, what its
components must be, to be able to perform the function that it does. (Interestingly,
a priori approaches to this type of question resembles the
transcendental inquiries found in Immanuel Kant's Critique of Pure Reason.)
In cognitive science this involves a conceptual mapping of the mind into
functional systems and sub-systems without an initial commitment to any specific
physical realization. This mapping leads to the idea of a modular mind, one
separated out by evolution into distinct systems with relatively narrow jobs to
do. The idea was developed for lower order cognitive activities in Jerry Fodor's
The Modularity of Mind, MIT Press (1983). Ironically Fodor is a strong
critic of Pinker's wider use of modularity in Pinker's How the Mind Works, Norton
(1999). See Fodor's The Mind Doesn't Work That Way, MIT Press. (2000).
I mention that Harris's work is stronger for being independent of all this
because first, she doesn't need it and second, it's philosophically
contentious. As Fodor mentions somewhere, we knew a lot about what hands and
fingers were for long before we knew anything about their evolution.

So how do identical twins raised in
the same household become so different? By extension, how do any siblings
become different. It's not parenting style. It's not birth order. Harris' story
proceeds something like the following. Every person's personality behavioral
traits are influenced, by three "systems" or dispositions (this is
beyond any genotypic influences). They are the relationship system, the
socialization system, and the status system. I will describe each.

The Relationship System: It is
certainly true that we collect and store data about the individuals that we
meet. Harris compares this to the "mental lexicon" by which we store
words and their meanings, here Harris takes her lead from Pinker. Our "people
lexicon" allows us to distinguish and recognize people as individuals, not
as class members, e.g., as my friend Antonia, not as an example of Italian,
women, communist. This involves things like face-recognition, but we are able
to take its cues from other things as well. People who are close to identical
twins have no trouble distinguishing them even if they don't know how they do
it. While the relationship system is a cognitive skill it is also a
motivational device. People are driven to collect information about other
people, and we don't need evolutionary speculation to seek agreement on the
existence of this intrinsic motivation. The relationship system guides our
behavior by supplying information about this or that individual.

The Socialization System: Having
identified individuals we must act in ways that are appropriate to who they
are. This system of instructions is the socialization system which tends to
make people of the same group more alike. Harris has a theory about how
socialization works. She notes studies that show that judgments of facial attractiveness
tend to regress to the mean. Show a person a group of facial photos of
strangers and they tend to prefer the one that has been artificially blended
from the others. On a conceptual level this blending creates prototypes that
define categories. Children have a motivation to categorize according to these
prototypes and to self-categorize in relation to others. Thus a young person
will categorize herself as girl or African-American or American or New Yorker,
etc. depending upon which prototype she is dealing with, and she will switch
behaviors accordingly. Socialization is self-motivated and takes place as the
adjustment of one's behaviors to the expectations of the central tendencies of
a category.

The Status System: Humans
everywhere compete with fellow group members. No reward system or external reinforcers
are necessary. The outcomes of that competition constitute status. Harris
relates studies that show that people react separately to social acceptance and
social status. Bullies can fail at acceptance but succeed at status and so can
have adequate self-esteem. Children by age six or seven have an idea, through pairwise
competitions, of their status in their groups. For boys, who's strongest,
fastest, toughest, etc. Harris believes that self-acceptance derives from the
status system (that portion that is not genetic) and, interestingly, that it is
adolescent status that is determining. She argues this on the basis that
adolescents that were tall relative to their peers make more money than those
peers when they are adults, regardless of their adult height. The idea is that
the earlier height-generated status conveyed a self-confidence that translated
into later "status-conferring" positions. The most conceptually
complicated part of determining one's own status is being able to read what
other's consider my status to be. This is a matter of picking up on sometimes
subtle clues involving the eye contact, posture, speech, etc. of others. It is
this system that shapes one's personality.

Genes have at least two types of
effects upon personality. There are direct affects where a child is born with
a certain level of aggressiveness, openness to change or shyness. And there
are indirect effects, for example, one's size, attractiveness or intelligence
affects the status others give to one, a status that is read from others and
internalized. But identical twins have identical genotypes and so these
factors do not come into play. Recall that Harris began the book promising to
explain the very different personalities of Lalah and Ladan, the identical,
conjoined Iranian twins. In this case the entire personality difference must
be explained by the three systems, particularly by the status system. How is
it that others formed different idea of the status positions of Lalah and Ladan,
ideas that were read off from these others by each of the twins? Here Harris
needs to fall back on singular (random) events. She seems a bit embarrassed by
this and is quick to note, "The incidents may be random but their
consequences are not (231)." An unusual and impressively correct answer
on a teacher's question can cause others to view you as "smart", a
belief that gains momentum in the eyes of others, is read from them into your
self-categorization, creating a confidence in academic matters that reinforces
others' status judgments, etc. This is Plomin's "gloomy prospect",
and its appearance is somewhat of a disappointment, almost as if an implicit
understanding about the rules of the game has been breached. I think of Lucretius'
first century BCE cosmology in which all atoms fall naturally in a straight
line toward the center of the universe. But to explain how a cosmos of
colliding atoms arose from this it was necessary for one of them to swerve,
ever-so-slightly. This swerve, a dues ex machima if there ever was one,
did not itself fall within the principles of Epicurean physics, but it
explained the origins of the motions that did. Paraphrasing Harris, the swerve
may have been random but its consequences were not. And later, in response to
Einstein's 1926 letter to Max Born where he assured us that, "God does not
play dice with the universe," Nils Bohr is reported to have said that
Einstein should, "Stop trying to tell God what he can do with his dice."
Researchers will likely seek the disappearance of the singular event as a
factor in the origins of personality differences at which time Bohr's God will need
to decide if they get their way.

This is a very important book. The
community of academic psychologists would do well to get over its arms-length response
to this outsider, Judith Harris, and to her sometimes quirkiness. Her
theoretical ideas about the environmental mechanisms of personal individuation
deserve the kind of rigorous investigation and testing that is the hallmark of
good science.

John D. Mullen is
professor of Philosophy at Dowling College in Oakdale, New York. He has
written a widely read text, Kierkegaard's Philosophy: Self-deception and
cowardice in the present age, Hard Thinking: A Reintroduction of logic
to everyday life, and co-authored with Byron M. Roth, Decision Making:
Its logic and practice.

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